Quantitative investigation of pengornithid enantiornithine diet reveals macrocarnivorous ecology evolved in birds by Early Cretaceous
The diet of Mesozoic birds is poorly known, limiting evolutionary understanding of birds’ roles in modern ecosystems. Pengornithidae is one of the best-understood families of Mesozoic birds, hypothesised to eat insects or only small amounts of meat. We investigate these hypotheses by collecting four lines of quantitative evidence: estimated body mass, claw traditional morphometrics, jaw mechanical advantage, and jaw finite element analysis. Each line of evidence was collected from an expanded sample of 192 extant birds to provide a comparative framework. Due to limited data, the diets of Eopengornis and Chiappeavis remain obscure. Pengornis, Parapengornis, and Yuanchuavis show adaptations for vertebrate carnivory. Thus, we consider specialisation for eating insects unlikely and propose meat as a major dietary component. Pengornis also has talons similar in shape and relative size to living raptorial birds like caracaras that capture and kill large prey, which represents the earliest known adaptation for macrocarnivory in a bird. This supports the appearance of this ecology ~35 million years earlier than previously thought. These findings greatly increase the niche breadth known for Early Cretaceous birds and makes an important step in shifting the prevailing view that Mesozoic birds mainly occupied low trophic levels.